This application claims the priority of 196 31 214.0, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a steering column for a motor vehicle, and more particularly, to a steering column having a steering spindle section which is deformable in an energy-converting manner in a crash, on a side acted upon by the impact, the steering spindle being displaceably disposed in an axial slide bearing and being held at the opposite end in an axial fixed bearing.
DE 23 16 515 A1 describes a flexible steering spindle having a targetedly shaped steering spindle section which can be deformed in a crash. On the side of a steering wheel, the steering spindle is clamped in a deformable bearing and, on the other side of the deformable steering spindle section, is held in another deformable axial fixed bearing. In the event of a strong axial loading of the steering wheel, a buckling of the steering spindle is achieved in this corrugated-tube-type steering spindle section. The steering spindle will then place itself with less resistance against the impact of an occupant onto the steering wheel. The impact energy reduced thereby is, however, low because the steering spindle section evades its deformation for the most part. An energy reduction along a longer displacement path of the steering spindle cannot be achieved in this known construction.
It is an object of the present invention to achieve a uniformly lasting impact energy reduction during a crash with a steering column.
This object has been achieved in accordance with the present invention by providing the deformable steering spindle section, on the side acted upon by the impact, at least one additional slide bearing radially supports the steering spindle in the motor vehicle.
The steering spindle is supported with the targetedly shaped steering spindle section which can be deformed in an energy-converting manner in a crash by two bearing points supporting the steering spindle and by a slide bearing, which also supports the deformable steering spindle section and guides it during the deformation. Thereby, a buckling of the steering spindle is prevented in the event of a high axial loading, in which the friction proportion in the slide bearing is only low with respect to the deformation work which is achieved in the deformable steering spindle section. Thereby, a uniform energy reduction is ensured along a long deformation path.
A slide bearing which can be manufactured in a simple manner and at reasonable cost minimizes the loading of an occupant in the event of an impact onto the steering wheel with optimal functioning of the deformable steering spindle section.
Furthermore, the energy reduction can be improved by a targetedly deformable steering spindle section in the lower steering spindle part by an advantageous bearing described above. Thereby, a steering wheel displacement in the direction toward the occupant by the intrusion of the forward structure can be prevented in a crash. A high-expenditure alteration of the steering spindle itself is not required for this purpose. In an assembly-friendly manner, the slide bearings and the fixed bearing can be combined in one piece in a fastening flange and can be jointly mounted in the motor vehicle.
With axial loading during a vehicle crash, a slip tube, as the deformable steering spindle section, can reduce energy because of its typical deformation capability. That is, one of the ends of the slip tube, at the slip-in end, is pressed through the slip-tube cavity, and the slip tube wall experiences a continuous deformation. The steering spindle is now additionally supported in the slide bearing close to the slip-in end of the slip tube so that the deformation of the slip tube can take place in a uniform and long-lasting manner. In order to avoid an initially increased resistance at the start of the deformation, the slip tube may have a bendable predeformation in the slip-in direction at the slip-in end.
By improving the guiding characteristics with the use of additional slide bearing, a simply constructed, deformable steering spindle section is achievable on the steering spindle, which can therefore also be molded in one piece into the steering spindle.
So that, the longitudinally displaceable section of the steering spindle obtains a well- sliding guide during its displacement, a ball cage can be provided in one or in several slide bearings and can be displaced with the steering spindle.